DEAR MISS MANNERS: If one attends a historical lecture and discovers the lecturer's information is factually wrong on most points, is there a polite time and manner in which one might point out more appropriate research materials?

I am a newcomer to this group and do not wish to cause offense, but historical medicine is a hobby of mine, and it riles me to have an "expert" pass off fantasy as history.

GENTLE READER: It is indeed churlish to correct a speaker, but you can certainly ask for clarification. As in: "I was always led to believe that treating disease with hot cups to correct the balance of the humors was no longer considered effective. Is there new evidence to show that it is?"